Define line ending style for different file types

Additionally, fix line endings on some files that were inconsistent
in this regard.

This gives a more consistent experience on all development
platforms.

All source files (be it scripts, makefiles, autoconf/automake
files,...) are given an explicit line ending style. For most
LF was chosen. Exceptions are typical windows scripts (.bat, .cmd,
.vbs,...) and some files related to the windows installer. Those
are fixed at CTRL/LF because the installer would have issues
otherwise).
The remainder of files are mostly plain text files (README's,
CHANGELOG's,...). These files are stored with LF line ending
in the repo, but checked out with the platform's native
line ending style. git takes proper care of the necessary
conversions automatically.

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@22712 57a11ea4-9604-0410-9ed3-97b8803252fd

.gitattributes

@@ -0,0 +1,44 @@
+# Default setting
+* text=auto
+
+# Files that should stay LF at all times
+*.am    text eol=lf
+*.c     text eol=lf
+*.chk   text eol=lf
+*.cpp   text eol=lf
+*.gnucash-xea text eol=lf
+*.h     text eol=lf
+*.hpp   text eol=lf
+*.html  text eol=lf
+*.i     text eol=lf
+*.in    text eol=lf
+*.m4    text eol=lf
+*.patch text eol=lf
+*.pl    text eol=lf
+*.po    text eol=lf
+*.py    text eol=lf
+*.qif   text eol=lf
+*.scm   text eol=lf
+*.sh    text eol=lf
+*.svg   text eol=lf
+*.xsl   text eol=lf
+
+Makefile.TAGS    text eol=lf
+Makevars         text eol=lf
+POTFILES.ignore  text eol=lf
+POTFILES.skip    text eol=lf
+configure.ac     text eol=lf
+custom.sh.sample text eol=lf
+glade-fixup      text eol=lf
+gnc-glossary.txt text eol=lf
+gnc-scm-info     text eol=lf
+
+
+# Files that should use CRLF at all times
+*.bat text eol=crlf
+*.cmd text eol=crlf
+*.isl text eol=crlf
+*.vbs text eol=crlf
+
+gnucash.iss.in text eol=crlf
+README*win32-bin.txt text eol=crlf